Over the past 20 years, the Gold Coast has seen unprecedented growth causing its existing excess recycled water release infrastructure to approach its capacity and capability. Thanks to the work of the Bothar team, the city’s recycled water infrastructure is now future proofed for the expected population increase over the next two decades.
Project specification
The installation of the new pipe was completed using a Herrenknecht AVN2000AB Tunnel Boring Machine (MTBM), with Bothar’s Project Manager Kieran O’Connor saying this could be the longest subsea microtunnelling drive completed in the southern hemisphere.
Bothar was also responsible for the temporary works design and construction of launch and retrieval shafts required for pipe jacking operations. The launch shaft at Quota Park in Biggera Waters was 26 m deep and 12.5 m diameter secant piled construction with the reception shaft – a 7.5 m diameter, 26 m deep pre-cast segmental sunk caisson – situated at South Stradbroke Island.
Mr O’Connor says Bothar was engaged to be the project’s specialist subcontractor on this critical seaway project.
First stages complete
In May, Bothar’s first MTBM resurfaced from its 1,385 m subsea crossing underneath the Gold Coast Broadwater, signalling the completion of the project’s first stage of tunnelling. Over the coming months, an AVN1500 – the project’s second MTBM – will be used to tunnel between Quota Park and O’Connell Park.
Both MTBM’s were manufactured by Herrenknecht and have been sourced from Bothar’s extensive international fleet of Herrenknecht machines.
Risk mitigation technology Mr O’Connor says the decision to use microtunnelling was born out of a need for risk mitigation considering the inherent technical, safety, environmental and community risks associated with the complex and challenging tunnel.
“Microtunnelling provided the optimal balance of innovation and risk mitigation,” he said.
“The subsea crossing was constructed underneath the seabed of an environmentally protected area of Moreton Bay providing for its continuous use by the local community for boating, fishing and recreational activities.”
In addition to the challenging tunnelling task, the hurdle of COVID-19 also arose during the project. To overcome social distancing restrictions and complete its essential project, Mr O’Connor says Bothar implemented strict protocols for its staff, including daily temperature testing and hygiene practices.
Bothar’s dedication to mitigating risks both to the environment and to its own workforce during the project demonstrates its commitment to finding a successful solution regardless of the challenges faced.
This article was featured in the September 2020 edition of Trenchless Australasia. To view the magazine on your PC, Mac, tablet or mobile device, click here.
For more information visit the Bothar Boring website.
If you have news you would like featured in Trenchless Australasia contact Assistant Editor Sophie Venz at svenz@gs-press.com.au